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rcu: add tracing for TINY_RCU and TINY_PREEMPT_RCU 

Add tracing for the tiny RCU implementations, including statistics on
boosting in the case of TINY_PREEMPT_RCU and RCU_BOOST.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2010-09-30 21:26:52 -07:00 committed by Paul E. McKenney
parent 24278d1483
commit 9e571a82f0
3 changed files with 226 additions and 11 deletions
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1
init/Kconfig
View File

@ -384,7 +384,6 @@ config PREEMPT_RCU
config RCU_TRACE
bool "Enable tracing for RCU"
depends on TREE_RCU || TREE_PREEMPT_RCU
help
This option provides tracing in RCU which presents stats
in debugfs for debugging RCU implementation.

4
kernel/rcutiny.c
View File

@ -144,6 +144,7 @@ static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
{
struct rcu_head *next, *list;
unsigned long flags;
RCU_TRACE(int cb_count = 0);
/* If no RCU callbacks ready to invoke, just return. */
if (&rcp->rcucblist == rcp->donetail)
@ -169,7 +170,9 @@ static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
list->func(list);
local_bh_enable();
list = next;
RCU_TRACE(cb_count++);
}
RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
}
/*
@ -252,6 +255,7 @@ static void __call_rcu(struct rcu_head *head,
local_irq_save(flags);
*rcp->curtail = head;
rcp->curtail = &head->next;
RCU_TRACE(rcp->qlen++);
local_irq_restore(flags);
}

232
kernel/rcutiny_plugin.h
View File

@ -23,12 +23,21 @@
*/
#include <linux/kthread.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#ifdef CONFIG_RCU_TRACE
#define RCU_TRACE(stmt) stmt
#else /* #ifdef CONFIG_RCU_TRACE */
#define RCU_TRACE(stmt)
#endif /* #else #ifdef CONFIG_RCU_TRACE */
/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
struct rcu_head **curtail; /* ->next pointer of last CB. */
RCU_TRACE(long qlen); /* Number of pending CBs. */
};
/* Definition for rcupdate control block. */
@ -90,8 +99,26 @@ struct rcu_preempt_ctrlblk {
u8 gpcpu; /* Last grace period blocked by the CPU. */
u8 completed; /* Last grace period completed. */
/* If all three are equal, RCU is idle. */
#ifdef CONFIG_RCU_BOOST
s8 boosted_this_gp; /* Has boosting already happened? */
unsigned long boost_time; /* When to start boosting (jiffies) */
#endif /* #ifdef CONFIG_RCU_BOOST */
#ifdef CONFIG_RCU_TRACE
unsigned long n_grace_periods;
#ifdef CONFIG_RCU_BOOST
unsigned long n_tasks_boosted;
unsigned long n_exp_boosts;
unsigned long n_normal_boosts;
unsigned long n_normal_balk_blkd_tasks;
unsigned long n_normal_balk_gp_tasks;
unsigned long n_normal_balk_boost_tasks;
unsigned long n_normal_balk_boosted;
unsigned long n_normal_balk_notyet;
unsigned long n_normal_balk_nos;
unsigned long n_exp_balk_blkd_tasks;
unsigned long n_exp_balk_nos;
#endif /* #ifdef CONFIG_RCU_BOOST */
#endif /* #ifdef CONFIG_RCU_TRACE */
};
static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = {
@ -170,6 +197,65 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t)
return np;
}
#ifdef CONFIG_RCU_TRACE
#ifdef CONFIG_RCU_BOOST
static void rcu_initiate_boost_trace(void);
static void rcu_initiate_exp_boost_trace(void);
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
* Dump additional statistice for TINY_PREEMPT_RCU.
*/
static void show_tiny_preempt_stats(struct seq_file *m)
{
seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n",
rcu_preempt_ctrlblk.rcb.qlen,
rcu_preempt_ctrlblk.n_grace_periods,
rcu_preempt_ctrlblk.gpnum,
rcu_preempt_ctrlblk.gpcpu,
rcu_preempt_ctrlblk.completed,
"T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)],
"N."[!rcu_preempt_ctrlblk.gp_tasks],
"E."[!rcu_preempt_ctrlblk.exp_tasks]);
#ifdef CONFIG_RCU_BOOST
seq_printf(m, " ttb=%c btg=",
"B."[!rcu_preempt_ctrlblk.boost_tasks]);
switch (rcu_preempt_ctrlblk.boosted_this_gp) {
case -1:
seq_puts(m, "exp");
break;
case 0:
seq_puts(m, "no");
break;
case 1:
seq_puts(m, "done");
break;
default:
seq_printf(m, "?%d?", rcu_preempt_ctrlblk.boosted_this_gp);
}
seq_printf(m, " ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n",
rcu_preempt_ctrlblk.n_tasks_boosted,
rcu_preempt_ctrlblk.n_exp_boosts,
rcu_preempt_ctrlblk.n_normal_boosts,
(int)(jiffies & 0xffff),
(int)(rcu_preempt_ctrlblk.boost_time & 0xffff));
seq_printf(m, " %s: nt=%lu gt=%lu bt=%lu b=%lu ny=%lu nos=%lu\n",
"normal balk",
rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks,
rcu_preempt_ctrlblk.n_normal_balk_gp_tasks,
rcu_preempt_ctrlblk.n_normal_balk_boost_tasks,
rcu_preempt_ctrlblk.n_normal_balk_boosted,
rcu_preempt_ctrlblk.n_normal_balk_notyet,
rcu_preempt_ctrlblk.n_normal_balk_nos);
seq_printf(m, " exp balk: bt=%lu nos=%lu\n",
rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks,
rcu_preempt_ctrlblk.n_exp_balk_nos);
#endif /* #ifdef CONFIG_RCU_BOOST */
}
#endif /* #ifdef CONFIG_RCU_TRACE */
#ifdef CONFIG_RCU_BOOST
#include "rtmutex_common.h"
@ -197,6 +283,7 @@ static int rcu_boost(void)
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED;
raw_local_irq_restore(flags);
rt_mutex_lock(&mtx);
RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++);
rt_mutex_unlock(&mtx);
return rcu_preempt_ctrlblk.boost_tasks != NULL;
}
@ -206,16 +293,27 @@ static int rcu_boost(void)
* the current grace period, and, if so, tell the rcu_kthread_task to
* start boosting them. If there is an expedited boost in progress,
* we wait for it to complete.
*
* If there are no blocked readers blocking the current grace period,
* return 0 to let the caller know, otherwise return 1. Note that this
* return value is independent of whether or not boosting was done.
*/
static void rcu_initiate_boost(void)
static int rcu_initiate_boost(void)
{
if (!rcu_preempt_blocked_readers_cgp()) {
RCU_TRACE(rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks++);
return 0;
}
if (rcu_preempt_ctrlblk.gp_tasks != NULL &&
rcu_preempt_ctrlblk.boost_tasks == NULL &&
rcu_preempt_ctrlblk.boosted_this_gp == 0 &&
ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) {
rcu_preempt_ctrlblk.boost_tasks = rcu_preempt_ctrlblk.gp_tasks;
invoke_rcu_kthread();
}
RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++);
} else
RCU_TRACE(rcu_initiate_boost_trace());
return 1;
}
/*
@ -231,7 +329,9 @@ static void rcu_initiate_expedited_boost(void)
rcu_preempt_ctrlblk.blkd_tasks.next;
rcu_preempt_ctrlblk.boosted_this_gp = -1;
invoke_rcu_kthread();
}
RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++);
} else
RCU_TRACE(rcu_initiate_exp_boost_trace());
raw_local_irq_restore(flags);
}
@ -258,10 +358,13 @@ static int rcu_boost(void)
}
/*
* If there is no RCU priority boosting, we don't initiate boosting.
* If there is no RCU priority boosting, we don't initiate boosting,
* but we do indicate whether there are blocked readers blocking the
* current grace period.
*/
static void rcu_initiate_boost(void)
static int rcu_initiate_boost(void)
{
return rcu_preempt_blocked_readers_cgp();
}
/*
@ -308,13 +411,14 @@ static void rcu_preempt_cpu_qs(void)
current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
/* If there is no GP then there is nothing more to do. */
if (!rcu_preempt_gp_in_progress() || rcu_preempt_blocked_readers_cgp())
if (!rcu_preempt_gp_in_progress())
return;
/* If there are blocked readers, go check up on boosting. */
if (rcu_preempt_blocked_readers_cgp()) {
rcu_initiate_boost();
/*
* Check up on boosting. If there are no readers blocking the
* current grace period, leave.
*/
if (rcu_initiate_boost())
return;
}
/* Advance callbacks. */
rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum;
@ -339,6 +443,7 @@ static void rcu_preempt_start_gp(void)
/* Official start of GP. */
rcu_preempt_ctrlblk.gpnum++;
RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++);
/* Any blocked RCU readers block new GP. */
if (rcu_preempt_blocked_readers_any())
@ -591,6 +696,7 @@ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
local_irq_save(flags);
*rcu_preempt_ctrlblk.nexttail = head;
rcu_preempt_ctrlblk.nexttail = &head->next;
RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++);
rcu_preempt_start_gp(); /* checks to see if GP needed. */
local_irq_restore(flags);
}
@ -747,6 +853,18 @@ void exit_rcu(void)
#else /* #ifdef CONFIG_TINY_PREEMPT_RCU */
#ifdef CONFIG_RCU_TRACE
/*
* Because preemptible RCU does not exist, it is not necessary to
* dump out its statistics.
*/
static void show_tiny_preempt_stats(struct seq_file *m)
{
}
#endif /* #ifdef CONFIG_RCU_TRACE */
/*
* Because preemptible RCU does not exist, it is never necessary to
* boost preempted RCU readers.
@ -802,3 +920,97 @@ void __init rcu_scheduler_starting(void)
#else /* #ifdef CONFIG_RCU_BOOST */
#define RCU_BOOST_PRIO 1
#endif /* #else #ifdef CONFIG_RCU_BOOST */
#ifdef CONFIG_RCU_TRACE
#ifdef CONFIG_RCU_BOOST
static void rcu_initiate_boost_trace(void)
{
if (rcu_preempt_ctrlblk.gp_tasks == NULL)
rcu_preempt_ctrlblk.n_normal_balk_gp_tasks++;
else if (rcu_preempt_ctrlblk.boost_tasks != NULL)
rcu_preempt_ctrlblk.n_normal_balk_boost_tasks++;
else if (rcu_preempt_ctrlblk.boosted_this_gp != 0)
rcu_preempt_ctrlblk.n_normal_balk_boosted++;
else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))
rcu_preempt_ctrlblk.n_normal_balk_notyet++;
else
rcu_preempt_ctrlblk.n_normal_balk_nos++;
}
static void rcu_initiate_exp_boost_trace(void)
{
if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks))
rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks++;
else
rcu_preempt_ctrlblk.n_exp_balk_nos++;
}
#endif /* #ifdef CONFIG_RCU_BOOST */
static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
{
unsigned long flags;
raw_local_irq_save(flags);
rcp->qlen -= n;
raw_local_irq_restore(flags);
}
/*
* Dump statistics for TINY_RCU, such as they are.
*/
static int show_tiny_stats(struct seq_file *m, void *unused)
{
show_tiny_preempt_stats(m);
seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen);
seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen);
return 0;
}
static int show_tiny_stats_open(struct inode *inode, struct file *file)
{
return single_open(file, show_tiny_stats, NULL);
}
static const struct file_operations show_tiny_stats_fops = {
.owner = THIS_MODULE,
.open = show_tiny_stats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static struct dentry *rcudir;
static int __init rcutiny_trace_init(void)
{
struct dentry *retval;
rcudir = debugfs_create_dir("rcu", NULL);
if (!rcudir)
goto free_out;
retval = debugfs_create_file("rcudata", 0444, rcudir,
NULL, &show_tiny_stats_fops);
if (!retval)
goto free_out;
return 0;
free_out:
debugfs_remove_recursive(rcudir);
return 1;
}
static void __exit rcutiny_trace_cleanup(void)
{
debugfs_remove_recursive(rcudir);
}
module_init(rcutiny_trace_init);
module_exit(rcutiny_trace_cleanup);
MODULE_AUTHOR("Paul E. McKenney");
MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
MODULE_LICENSE("GPL");
#endif /* #ifdef CONFIG_RCU_TRACE */